\name{ggbiplot}
\alias{ggbiplot}
\title{Biplot for Principal Components using ggplot2}
\usage{
  ggbiplot(pcobj, choices = 1:2, scale = 1, pc.biplot =
  TRUE, obs.scale = 1 - scale, var.scale = scale, groups =
  NULL, ellipse = FALSE, ellipse.prob = 0.68, labels =
  NULL, labels.size = 3, alpha = 1, var.axes = TRUE, circle
  = FALSE, circle.prob = 0.69, varname.size = 3,
  varname.adjust = 1.5, varname.abbrev = FALSE, ...)
}
\arguments{
  \item{pcobj}{an object returned by prcomp() or
  princomp()}

  \item{choices}{which PCs to plot}

  \item{scale}{covariance biplot (scale = 1), form biplot
  (scale = 0). When scale = 1, the inner product between
  the variables approximates the covariance and the
  distance between the points approximates the Mahalanobis
  distance.}

  \item{obs.scale}{scale factor to apply to observations}

  \item{var.scale}{scale factor to apply to variables}

  \item{pc.biplot}{for compatibility with
  biplot.princomp()}

  \item{groups}{optional factor variable indicating the
  groups that the observations belong to. If provided the
  points will be colored according to groups}

  \item{ellipse}{draw a normal data ellipse for each
  group?}

  \item{ellipse.prob}{size of the ellipse in Normal
  probability}

  \item{labels}{optional vector of labels for the
  observations}

  \item{labels.size}{size of the text used for the labels}

  \item{alpha}{alpha transparency value for the points (0 =
  TRUEransparent, 1 = opaque)}

  \item{circle}{draw a correlation circle? (only applies
  when prcomp was called with scale = TRUE and when
  var.scale = 1)}

  \item{var.axes}{draw arrows for the variables?}

  \item{varname.size}{size of the text for variable names}

  \item{varname.adjust}{adjustment factor the placement of
  the variable names, >= 1 means farther from the arrow}

  \item{varname.abbrev}{whether or not to abbreviate the
  variable names}
}
\value{
  a ggplot2 plot
}
\description{
  Biplot for Principal Components using ggplot2
}
\examples{
data(wine)
wine.pca <- prcomp(wine, scale. = TRUE)
print(ggbiplot(wine.pca, obs.scale = 1, var.scale = 1, groups = wine.class, ellipse = TRUE, circle = TRUE))
}

